1. Field of the Invention
This invention relates to a hand tool, and more particularly to a ratchet device.
2. Description of the Related Art
Referring to FIG. 1, a conventional ratchet device disclosed in Taiwanese Patent No. M342913 includes a mounting member 1, two pawl members 2 mounted to the mounting member 1, a U-shaped resilient member 3 mounted to the mounting member 1, a direction-switching ring 4 sleeved on the mounting member 1, and a ratchet wheel 5 sleeved on the mounting member 1. The mounting member 1 has a U-shaped groove 101 for receiving the resilient member 3, and two accommodating grooves 102 located respectively at two sides of the U-shaped groove 101 for receiving the pawl members 2, respectively. The direction-switching ring 4 has an inner peripheral surface 401 and two positioning grooves 402 formed in the inner peripheral surface 401 and aligned respectively with the pawl members 2. The ratchet wheel 5 has a plurality of teeth 501. When the switching member 4 is disposed at a middle position, the pawl members 2 are biased by free ends 301 of the resilient member 3 to engage the positioning grooves 402, respectively, and engage the teeth 501 of the ratchet wheel 5. At this time, the ratchet wheel 5 can be rotated in two directions through operation of the mounting member 1.
When the switching member 4 is rotated in a direction, such that one of the pawl members 2 is pressed by the inner peripheral surface 401 to separate from the teeth 501, and the other of the pawl members 2 remains within the corresponding positioning groove 402 and engages the teeth 501, the ratchet wheel 5 is rotatable in only a single direction.
The aforesaid conventional ratchet wheel suffers from the following drawbacks:                1. Each of the pawl members 2 engages only one of the teeth 501, thereby affecting adversely transmission of power from the mounting member 1 to the ratchet wheel 5.        2. During unidirectional rotation of the ratchet wheel 5, force is transmitted from one pawl member 2 to one tooth 501. As a result, serious wear is experienced by the one pawl member 2 and the one tooth 501, thereby reducing the service life of the ratchet device.        3. When a force is applied to rotate the switching ring 4, it must be large enough to overcome the biasing force of the resilient member 3, thereby resulting in difficulties during the direction switching operation.        